The dark patches below the eyes are due to the collection of blood in the layer below the skin (bruise). It shall take a few days, usually 5-7 days, for the blood to be absorbed and nothing needs to be done. In case of recent injury, ice packs are advised to reduce the accumulation of the blood.

I suggest you to consult an orthopaedician nearby for a detailed examination. You may get the X-ray of the area affected under his/her guidance.

In the interim, ice the affected area and take anti-inflammatory drug like motrin to reduce pain and inflammation.

Hope I have answered your query. Let me know if you have any more concerns.